Investigation of environmentally driven deterioration of the Great Sphinx and concepts for protection

Abstract

The micro-environment of the Great Sphinx at Giza in Egypt was quantified by continuous monitoring over a three-year period of the climate at the site and the relative humidity and temperature within the stone of the monument. Environmental factors that potentially drive deterioration mechanisms were recorded, including thermal cycling, wind, nightly dew-fall on the monument and rainfall, and the role of these factors in weathering is discussed. A significant finding was the large daily change in temperature relatively deep within the stone of the Sphinx. Cycles of wetting from dew-fall and drying are an important cause of flaking of the limestone on horizontal and near-horizontal surfaces. The concept of using a night-time shelter for temporary protection of the monument from dew condensation and wind erosion is presented as an alternative to treatments such as consolidation or desalination of the stone.